Of the Old-Ir. forms dono arose from dano, as ocus from
acus, under the influence of the u-shaded `n.' At the time
of the Würzburg Glosses dano was still kept distinct from
dono, the latter being used after interrogatives apparently
as an enclitic, without accent:
ar cia dono,
Wb. 2 d 10
.
cepu dono,
7 d 16
.
ce dono,
8 d 15
(cf.
cid dono,
Laws i 48.
24
;
54. 3 f.b.
).

The syncopated Mid.-Ir. forms dno, no retaining
`o' show that also in Old-Ir. the stress fell on the ultimate,
as dano stressed on the penultimate would have given Mid.-
Ir. dana. The Mid.-Ir. writing denu (
RC xii 72 § 44
, cf.
dechum, debert) points in the same direction. Compare
also the writing doná in the FM. In poetry the accent
falls on the ultimate:

Acall. 3852
: mairg dadhair don luing dana.
nachasainic Tonn Chlidna.

The syncopated form is often used in poetry for the convenience of the metre. It appears in several poems
ascribed to poets of the 11th and 12th centuries, e.g.—

LL 144 a 9
: Almon rathuit artús dā (dno leg.)
i nEtail ra Troiano.

(a poem by Giolla an Choimdhedh Ua Cormaic of the early
12th century).

This brings us back to the time of the Codex Sangallensis;
whence it follows that dno, though not occurring in any
MS older than the LU, belongs to the Old-Ir. period.—
No was developed from dno in Mid.-Ir. time. It seems
impossible to fix the date of this development accurately.
The appearance of `no' in old poetry, as
BB 46 a 19
,
297 b 42
,
is no test, as no might be a late substitute for dno. The
fact that the earliest instances occur in the LL points to the
12th century. In Mid.-Ir. MSS dā, dno, and no go hand
in hand. The spoken form was dno, later no; but the
traditional writing dā lingered on for centuries in the MSS.
No is found in MSS from the early 13th to the 15th
century, when it became obsolete. The FM write doná,
dana, dna, purely literary forms. In the Annals of Ulster
the particle does not in any form occur after the year 1204
(
AU ii 242. 2
).

In Mid.-Ir. no syntactical distinction is made between
dā, dno, dna, and no. The particle is never placed at the
head of the sentence, but can, apart from this, occupy
almost any position within it. It follows stressed and
unstressed words, and appears particularly often after
emphasising particles, a circumstance which contributed
to the syncope of the first syllable. It gives a certain
emphasis to the accented word immediately preceding.
The following is a synopsis of the most common positions
of the particle:

IITherefore, then, accordingly, itaque, et ita, igitur—
both in principal and secondary clauses, drawing a conclusion
from what has been said before. By the Irish
themselves translated by ergo, igitur, ita (locus ergo, locus
igitur, sic igitur, no ita (
ACL iii 293. 16
) = loc dā, amlaid
dā, nó dā). Common in the Glosses, esp. with imperative
and in prohibitions, but rare in all Mid.-Ir. MSS.—

III Very common in progressive description or narrative,
indicating temporal and logical sequence: then, accordingly,
so, uponwhich, thereupon, now. This usage arose from I,
the original sense `further, again' being still perceptible.